Ferrous alloy and process of prodcing ferrous alloy



\ April 13,1937. c. F. LAUENSTEIN 2,077,116

FERRoUs ALLOY AND PROCESS OF PRODUCING FERROUS ALLOY Original FiledApril '7, 1953 3 v [five/727507 izriflaaemsezh Patented Apr. 13, 1937 4UNITED sTATEs PATENT OFFICE.

FEBROUS ALLOY AND PROCESS OF DUCING FERROUS ALLOY Pao- Carl F.Lanenstein, Indianapolis, Ind., assignor to Link-Belt Company, Chicago,111., a corporation of Illinois Original application April I, 1933,Serial No.

Divided and this application December 13, 1934, Serial No. 757,289

6 Claims.

This application is a division of my co-pendin application Serial Number664,902, filed April 7, 1933, which is itself a continuation in part ofmy application Serial Number 475,829, filed August This inventionrelates to a ferrous alloy and to the process of producing it. The rawmaterial from whichthe metal is produced is essentially malleableizedcast iron which contains certain l strengthening alloying elements. Manyalloying materials may be used. In the present case I am concernedprimarily with the use of manganese,

molybdenum, chromium and vanadium which,

when alloyed with the iron, form carbides, and

1 may, therefore, be included in the carbide forming group of alloys". Ihave also used, however, nickel, copper and aluminum.

As generally understood, ordinary malleableized cast iron is granular inits structure, being com 20 posed mainly of grains of ferrite and smallparticles of carbon or graphitic carbon. One' 35 the specification andclaims.

The metal of the present invention is formedfrom white .cast iron.Before the commencement of my process the iron is put through anystandard or suitable malleableizing process. White cast iron has anaverage chemical compositionas follows: 1

v Per cent Combined carbon 2.30-2.40 Graphitic carbon. Nil Silicon .90-.95 Manganese .27 Sulphur '.060 Phosphorous .16

To this may be added suitable quantities of copper, molybdenum, nickel,manganese, chromium, vanadium, aluminum or other alloying elements.These alloying elements may be added into the cast iron in the furnaceor the ladle, or .55 at any time before the iron is finally molded.

Another object is to produce a metal and a;-

The presence of the alloying elements The white cast iron with thealloying elements is poured into suitable molds and allowed to cool. Itmay then be cleaned and after cleaning it is put through any suitablemalleableizing process.

After the malleableizing process is completed a subsequent heattreatment is applied to themetal. This heating will usually be done infurnaces, but may, of course, be done by any other means. The iron israised to a temperature between 1375 F. and 1500 F. This temperature isgiven as approximating the best temperature, but a variation eitherabove or below this temperature is possible. After the material hasreached the critical or carbon combining temperature a part of thecarbon is combined with ferrite. The length of time that the materialbeing treated must be held at this temperature varies .with the size ofthe parts being treated and "with the physical properties desired. Afterthe heating has been carried on a sufficient time, the parts are thenquenched, that is to say, cooled, in air, oil,

water or other medium. In ordinary practice, no

particular effort is made to cool the metal slowly and where it isquenched in oil or a liquid, it, is

.usually cooled rapidly. Where it is desired to give the metal a toughand wear resisting outer coat, the heating operation will be carried outin the presence of a carburizing agent.

When the material being treated has been first heated and quenched, itis thereafter reheated to a temperature not exceedingrthe critical orcarbon combining temperature. The result of this second heating is tocausethe martensite or troostite retained after the first heating tobreak down into pearlite or sorbite. This change will normally beeffected at a temperature range of 900 F. to 1350" F. The cooling, afterthe second heating, is preferably air cooling although a water or oilquenching may be used, depending somewhat upon the physical propertiesdesired. A water quenching produces a stiffer, higher strength iron,while oil and air cooling produces relatively more ductile iron. Anycooling method may be used.

The accompanyingdrawing illustrates in Figure 1 the structuralarrangement and constituents of a sample of malleableized cast iron andin Figure 2 a sample of the metal of my -invention. The figures arediagrammatic showings based upon microphotographs of samples of metals.They suggest diagrammatically only typical forms of the metal. Othersamples would show the same general characteristics, but would showdetailed modifications.

In Figure 1 the metal is seen to be generally granular. It is composedof grains, A, which are ferrite and separated from each other alongboundaries B. The grains may be of irregular shapes and sizes.interspersed through the mass of' the metal are spots of free orgraphitic carbon C.

Figure 2 is a diagram based upon a microphotograph of a section of asample of the metal of this invention.

Dis illustrated in the drawing, the metal is genially granular, beingformed of grains A. These grains are bounded or separated alongboundaries B. The grains are in the form of ferrite. C represents a spotof graphitic or free carbon. In a larger area of the metal, a number ofsuch spots of graphitic carbon would appear. Situated throughout themetal, surrounding the grains and the graphitic carbon and filling thegreat majority of the grain boundaries and to some degree penetratingwithin the ferrite grains themselves is pearlite. This material isindicated at D.

Figure 2 illustrates an important characteristic of the presentinvention, namely, that there is distributed throughout the metal, alongthe grain boundaries and about such particles of graphitic carbon as arepresent, an agent which tends to stiffen the grains and prevent theirdistortion under stress, thus strengthening the mass and preventing theseparation or pulling apart of the'grains. This agent is an iron carbidewith alloy content and in the form illustrated in Figure 2, is normallypearlite or sorbite. It is characteristic of this iron carbide, which inthis case may be pearlite or sorbite, that it is strong and tough and itthus strengthens the grains against distortion, holding the grainstogether more strongly than in other cast iron where the ferrite iscombined without the presence of any appreciable amounts of alloypearlite at the grain boundaries. It thus increases the tensileproperties of the material. 7

It also makes the metal of the invention highly resistant to wear orabrasion. The harder and tougher alloy pearlite or alloy sorbite at theferrite grain boundaries acts as a guard preventing the wearing orabrading away of the softer ferrite grains. The pearlite or sorbite isstrengthened by the alloying element.

In the metal of this invention, the main body of the metal is made up ofa group of ferrite grains. The great'majorityof these grains issurrounded each with a harder shell of pearlite or sorbite, that is tosay, with a shell of an iron carbide with alloy content which has suchphysical properties that it tends to strengthen the grains of ferrite.It prevents deformation of the grain and by this fact it resistsdistortion of the grain and resists breaking of the grain itself orseparation of one grain from'the other. This iron carbide in the body ofthe metalmay be said to act like an iron reinforcement about a piece ofwood. It prevents distortion and so'prevents splitting and breaking.Thus in the metal of this invention there is built up throughout thebody of the metal a reinforcing framework of the stronger iron carbidewhich has many cell-like compartments in it. These cells surround theweaker grains of the ferrite which are thus strengthened and theseparation of these ferrite grains is resisted by this cell likestructure of the carbide. In effect there is built up a structure whichmay be likened to a honey comb. This is formed of the iron carbide andwithin the cells of the honey comb are found the grains of ferrite. Thehoney comb thus serves to st e g the mass as a whole and to preventseparation of the grains.

As above indicated, the metal owes its strength to the presence of thepearlite or some form of iron carbon alloy network surrounding thegrains and lying within and along the grain boundaries. The presence ofthe alloying metal gives this network a higher strength and hardnessthan that which it would otherwise have if the alloying element were notpresent.

The temperature ranges above suggestedare not absolute limits and areindicated for the first heating as being within the range of thecritical or carbon combining temperature, and for the second heating asbeing above the range of customary hot galvanzing. In the first heatingthe temperature may be as high as 1500" F. and in the second heating itmay be as low as 900 F., although in normal practice the first heatingis preferably between 1425 F. and 1450 F. and the second heating ispreferably between 1200- F. and 1250 F.

The increased strength of my metal resultant from the use of thealloying element is possibly caused by the pearlite or sorbite,including such an alloy content, having higher physical properties thanpearlite or sorbite without this alloy content. This higher strengthpearliteor sorbite formed at the grain boundaries has a greaterstiifeningeifect on the ferrite grains and better resists theirdeformation under stress, thus producing a higher strength metal. Sincethe physi-' cal properties of this alloy pearlite or sorbite net workcan be varied by different heat treatments I and by the use of diiferentalloys or different combinations of alloys, the resultant properties ofmy metal can also be so varied.

The alloying m erials above mentioned are only given as typic l metalsfor this use. Many others might be used. For some purposes one will beused along and for other purposes two or more will be used together.Thus "one alloy might include manganese, .50 per cent. Another alloymight include molybdenum up to .50 per cent or vanadium up to .60 percent. These are given as merely typical of possible alloys. One or moreof the alloying substances of the carbide forming group may be used inthe metal. Thus a very wide variety of alloying elements and combina-'tions of these elements may be used in myinvention.

In general, the typical alloying elements and the quantities of themwhich are most likely to be used are as follows:

Percent Manganese .50 to 1.00 Molybdenum .20 to .60 Chromium -1... .10to .60. Vanadium .10 to .60

able iron. In some cases the alloy content may necessitate slightvariations from the standard. One typical annealing cycle may be asfollows: Heat the metal to 1650 F., this heating occupy ing about 36hours: hold the metal at 1650 F. for 36 hours. 'Cool to 1200 F. at 6 F.per hour, occupying about '72'hours. The furnace may then be unloadedand after cooling and inspection the castings or other metal articlesmay be' put 10 through the secondary heat treating cycle. Changes intemperatures and times of heating may be desirable or may be necessarywhere alloying metals are used or where they are used in diiferentproportions. Some of the elements listed do not have such a markedeifect on the critical temperature but in general tend to raise itslightlyl It is therefore possible to use an alloy which depresses thecritical temperature, and add to it an alloy which has a slightlyopposite or cancelling efiect, and use a first treating temperature of1450" F. In any event, the treating temperatures mustbe governed by thealloying elements and the desired physical properties in the finishedpart.

mally be used, while a second heating of 12W F.

,to 1250" F. would normally be when molybdenum is used alone, theinitial heating temperature is normallyin the neighborhood of 1475F.-and the second heating temperature in the neighborhood of 12001. Asuitable analysis a of an alloy involving two oi. the carbide forminggroup is as follows! Percent Carb 2.30 to 2.40 Silicon .90 to .95Manganese .27 Sulphur -.06 Phosphorous .16 Molybdenum .30

Such an alloy would preferably be heat treated by heating toapproximately 1500 F., quenching in oil and subsequently reheating to atempera- When used alone, manganese tends to lowerthe criticaltemperature and an initial heating temperature of 1425 F. to 1475 F.would not I claim: 1. A granular ferrous metal, including an alloyingelement of the carbide forming group of elements consisting ofmanganese, molybdenum,

chromium and vanadium in approximately the following proportions:Manganese .50 to 1.0 per cent; molybdenum .20 to .60 per cent; chromium.10 to .60 per cent and vanadium .10 to .60 per cent, and includingferrite, graphitic carbon and iron carbide, the latter being distributedalong the grain boundaries and between the grains of ferrite and aboutthe graphltic carbon.-

2. A granular ferrous metal, including at least one of the alloyingelements of the carbide-forming group of elements consisting ofmanganese, molybdenum, chromium and vanadium in approximatelythe'following proportions: Manganese .50 to 1.0 per cent; molybdenum .20to .60 per cent; chromium .10 to .60 per cent and vanadium .10 to .60per cent, and including grains of ferrite, graphitic carbon and ironcarbide, the latterbeing distributed along the grain boundaries-andbetween the grains of ferrite and about the graphitic carbon.

3. A ,granularferrous metal having an alloying 'lelement and includinggrains of free ferrite, giaphiticcarbon and iron carbide, the latterbeing distributed along the grain boundaries and between the rains offerrite and about the graphitic carbon, said alloying element beingmolybdenum, from .20 per cent to .60 per cent.

4. A granular ferrous metal having an alloying element and includinggrains of free ferrite, graphitlc carbon and iron carbide, the latterbeing distributed along the grain boundaries and between the grains offerrite and about the graphitic carbon, said alloying element beingmangane se, from .50 per cent to 1.00 per cent.

5. A granular ferrous metal having an alloying element and includinggrains of free ferrite, graphitic carbon and iron carbide, thelatterbeing distributed along the grain boundaries and between the rainsof ferrite and about the graphitic carbon, said alloying element beingchromium, from .10 per cent to .60 per cent.

6.'The process of heat treating malleableized cast iron, which ironincludes an alloying element of the carbide forming group of elementsconsisting of manganese .50 to 1.0 per cent; molybdenum .20 to .60percent; chromium .10 to .60 per cent and vanadium .10 to .60 per cent,which process includes heating the iron to a point between 1375" F. and1500 F., quenching and reheating to a point between 900 F. and l350 F.

CARL F. LAUENSTEIN.

